1. Field of the Invention
Embodiments of the invention relate to optical semiconductor-based lighting apparatuses.
2. Discussion of the Background
Generally, fluorescent lamps and incandescent lamps are used as a light source for lighting. Incandescent lamps have low economic feasibility due to high power consumption and thus demand for incandescent lamps continues to decrease. Further, it is predicted that this trend will continue into the future. On the contrary, fluorescent lamps have higher economic feasibility due to low power consumption, which is about ⅓ that of incandescent lamps. However, fluorescent lamps require application of high voltage, causing a blackening phenomenon and shortening the lifespan thereof. Further, mercury injected together with argon gas into a vacuum glass tube of a fluorescent lamp is toxic and environmentally harmful.
Recently, needs for LED lighting apparatuses employing an LED as a light source have been rapidly increased. The LED lighting apparatus has long lifespan and requires low power for operation. Further, the LED lighting apparatus does not use a toxic substance such as mercury, thereby guaranteeing environmental friendliness.
Recently, a semiconductor optical device, such as a light emitting device (LED), is increasingly used as a light source of a lighting apparatus, such as a factory lighting fixture, street lamp, security light, and the like, which require high light output. Such a lighting apparatus generates large amounts of heat during operation of a light emitting module including semiconductor optical devices.
Typically, a conventional optical semiconductor-based lighting apparatus is provided with a heat sink disposed to adjoin a heat sink base or a printed circuit board (PCB), on which semiconductor optical devices are mounted, to dissipate heat. However, it is recognized that such a conventional lighting apparatus suffers from many restrictions in improvement of heat dissipation efficiency through the heat sink. To solve such a problem, various studies and efforts have been made to apply a heat pipe structure for heat dissipation using fluid for absorption and discharge of heat to an optical semiconductor-based lighting apparatus.
In one conventional lighting apparatus, the heat pipe structure is disposed to adjoin a rear side of a heat sink base to promote heat dissipation, but provides limited improvement of heat dissipation efficiency due to a small surface area at a heat dissipation side. In addition, when applying the heat pipe structure to the rear side of the base of the light emitting module including semiconductor optical devices arranged thereon, a relationship between arrangement of the semiconductor optical devices and the heat pipe structure is not considered in the art. Further, since a fluid containing pipe is used as the heat pipe, there are many limits in suitable positioning of the heat pipe structure on the rear side of the heat sink base due to restrictions in pipe design and processing, and interference between the heat pipes.
Further, in another conventional lighting apparatus, a power supply such as a switching mode power supply (SMPS) is received within a housing. When AC current is supplied from outside, the SMPS converts the AC current into DC current and supplies the DC current to the semiconductor optical devices of the light emitting module in the housing. However, since the power supply such as SMPS generates large amounts of heat during operation and the heat remains at an upper housing section, there is a need for efficient cooling of the SMPS.
The optical semiconductor-based lighting apparatus is applied to lighting fixtures at places such as factories, where severe scattering of dust or fine particles occurs. Although the optical semiconductor-based lighting apparatus includes an optical member made of glass or synthetic resin to protect a light source from the surroundings, various kinds of foreign matter including dust and fine particles in such a poor environment are likely to adhere to the optical member, causing a reduction in light output. Therefore, there is a need for a technique that facilitates removal of foreign matter from the optical member.